Balloon with dividing fabric layers and method for braiding over three-dimensional forms

ABSTRACT

A medical balloon with a variable diameter that is reinforced with continuous fibers woven to form a fabric with a varying number of layers and fiber densities. Portions of the balloon having a relatively smaller diameter are reinforced with a fabric having a reduced fiber density and an increased number of layers to facilitate the placement of the layers. The fabric also includes a braiding pattern that facilitates the transition from a single layer fabric to a multiple layer fabric. Also described is a manufacturing method for the braiding and layering.

PRIORITY DATA AND INCORPORATION BY REFERENCE

This application is a continuation of prior U.S. patent application Ser.No. 12/517,450, filed on Jun. 3, 2009 now U.S. Pat. No. 8,122,809, whichis the national stage of PCT/US2007/087815, filed Dec. 17, 2007, whichclaims priority from U.S. Provisional Patent Application Ser. No.60/870,479 filed Dec. 18, 2006, the disclosures of which areincorporated herein by reference.

TECHNICAL FIELD

The present invention relates to methods and apparatus for braidingfibers over three-dimensional shapes. In particular, the inventionrelates to the reinforcement of balloons with weaved fibers and fabrics.

BACKGROUND ART

In the medical balloon art, medical balloons have been reinforced byplacing fibers into pre-determined arrangements using manual orpartially automated processes, as described in U.S. Pat. No. 6,746,425,which is incorporated by reference in its entirety. Some manual andpartially automated manufacturing processes require the manualmanipulation of fibers to properly dispose the fibers in the desiredlocation of the balloon. The non-automated aspects of such processesincrease the cost and time investment to manufacture a reinforcedmedical balloon as compared to highly automated processes. Also, thenon-automated aspects of such processes, and the time associated withmanual processes, prevent or impede the formation or efficientdisposition of complex fiber patterns, or the formation of complex weavepatterns that facilitate the disposition of a two-dimensional fabricover a three-dimensional contour associated with a medical balloon. Itis also believed that automated processes facilitate a more precise andconsistent disposition of fibers that is either impossible or difficultto achieve with manual or partially automated processes.

Braiding technologies and 2D and 3D braiding machines are described in:“Braiding,” 2005 Advanced Composite Materials & Textile ResearchLaboratory, University of Massachusetts-Lowell, available at theUniversity of Massachustts-Lowell's Advanced Composite Materials &Textile Research website. Braiding technologies and Cartesian braidingmachines are described at the website of 3TEX, Inc. A report by theNational Textile Center (NTC) of Springhouse, Pa. describes braidingpatterns and describes the behavior of braids under tensile load, andthe effect of yarn angle with respect to load and jamming condition, in“Engineered Non-Linear Elastic Blended Fabrics,” NTC Project F00-PH052005. The following articles describe braids: Guang-Wu Du, Tsu-Wei Chou,and P. Popper, “Analysis of three-dimensional textile pre-forms formultidirectional reinforcement of composites,” J. Mater. Sci. 26 (1991)3438-3448; M. Dunn, E. Armstrong-Carroll, Y. Gowayed; “EngineeredNon-linear Elastic Bland Fabrics”; W. Seneviratne, J. Tomblin, “DesignOf A Braided Composite Structure With A Tapered Cross-Section,” NationalInstitute for Aviation Research Wichita State University Wichita, Kans.67260-0093; and The Department Of Defense Handbook Composite MaterialsHandbook Volume 2, “Polymer Matrix Composites Materials Properties.Braiding technology is also described in U.S. Pat. Nos. 5,718,159,5,758,562, 6,019,786, 5,957,974, 4,881,444, 4,885,973, and 4,621,560.Each of the above-identified references are incorporated by referenceherein.

For medical balloons, very thin walls are desirable. To reduce wallthickness, it is necessary to reduce the thickness of each fiber andincrease the number of fibers to supplement for the reduced strength ofthe thinner fibers. If the thickness of the fibers is reduced, it isnecessary to increase the number of fibers, and the fiber density, bythe square of the reduction in thickness, in order to maintain the sametensile strength in the reinforced balloon wall. It is believed that thereduction of fiber thickness leads to a problem when the fibers arebraided. This is because of the bunching or jamming effect that occurswhen a continuous braided fabric is disposed over a cylindrical portionof a balloon and then continued over a portion of the balloon with areduced diameter, such as when a fabric extends from a cylindricalballoon form to a conical end of the balloon. It is also believed thatthe same problem exists when a fabric is disposed over anythree-dimensional object that reduces from one diameter to a smallerdiameter.

At the conical end of a balloon, the fiber density increases as thediameter of the balloon decreases, as the same number of fibers are madeto cover a decreasing circumferential area. If the weave pattern ischanged to allow for a lower fiber density at the areas of reduceddiameter, the wall thickness can become too thin and a transition to adifferent fiber angles in the weave can cause the fibers to bunch or jamand prevent further reduction in balloon diameter. Also, sparse braidingprovides for greater spacing between fibers and thereby increase thejamming angle between fibers, and wall thickness is sacrificed in themain part of the balloon because of the inverse square relationshipbetween the wall thickness and the fiber density required to achieve aconstant wall strength. In other words, the fibers need to get thickerto maintain the reinforced strength per unit area of the balloon wall.As a result, the fiber density limitation at the balloon ends dictates asub-optimal fiber density—and concomitant wall-thickness—over thecentral region of the balloon where the diameter is largest.

DISCLOSURE OF INVENTION

A structure and method for making a fiber-reinforced balloon for medicaltreatments such as percutaneous transluminal coronary angioplasty(PTCA), and delivery of a vascular stents or stent grafts, that isamenable to automated manufacture and that permits fiber angles to beoptimized for holding pressure.

In the embodiments described herein, a continuous fiber wind is weavedto make a fabric that reinforces a balloon with a varying diameter whileminimizing jamming of the fabric as the fabric transitions from coveringa large diameter portion of the balloon to a smaller diameter portion ofthe balloon. A braiding pattern is used that transitions from a singlelayer to multiple layers as the fabric transitions to smaller diameterportions of the balloon. When the single layer fabric transitions to amultiple layer fabric, the fiber density of the single layer fabric isreduced in each of the multiple layers as each fiber of the single layeris directed to one of the multiple layers. When two or more layers areformed from a single layer, the fiber density of the innermostreinforcing later of the balloon can be controlled to minimize jammingor bunching of the woven fabric. The fiber densities of the layersformed proximate to the innermost layer, when the innermost layer isformed, can also be controlled to permit the composite layering of theballoon as the diameter of the balloon decreased. The dividing of thesingle layer fabric into multiple layers thus facilitates a balloon tobe reinforced with fibers that extend across the entire balloon and intoportions of the balloon with variable diameters, thereby facilitatingthe automated fabrication of a reinforced balloon. The dividing of asingle layer also facilitates disposition of multiple reinforcementlayers at reduced diameter portions of a balloon with minimized bunchingof fabrics due to increased fiber density.

In one embodiment, the medical balloon includes first and second fibersthat together define a main fabric layer that reinforces a main portionof the balloon, with the first fibers defining a first fabric layer thatreinforces a first portion of the balloon and the second fibers defininga second fabric layer that reinforces the first portion of the balloon,and with the first fiber layer separate from and disposed adjacent tothe second fiber layer.

In another embodiment, the medical balloon includes first and secondfibers that at least in part interweave together to define a main layerthat reinforces a main portion of the balloon, with the first fibersdefining a first layer that reinforces a first portion of the balloon,with the second fibers defining a second layer that reinforces the firstportion of the balloon, and with the first fiber layer separate from anddisposed adjacent to the second fiber layer.

In yet another embodiment, the medical balloon includes a main fabriclayer reinforcing the balloon, a first fabric layer contiguous with andextending from the main fabric layer to reinforce the balloon, and asecond fabric layer contiguous with and extending from the main fabriclayer to reinforce the balloon, with the first fabric layer disposedseparate from and adjacent to the second fabric layer.

In still another embodiment, the medical balloon includes a main fabrichaving a main braid pattern of interweaved first and second fibers thatreinforce the balloon, a first fabric having a first braid pattern ofthe first fibers, and a second fabric having a second braid pattern ofthe second fibers, with the first and second fibers joining the mainfabric to the first and second fabrics.

In another embodiment, the medical balloon includes a central section ofthe balloon with a first outer diameter, a tapering end of the balloonwith a second outer diameter that is less than the first outer diameter,a main fabric with interweaved first and second fibers and with the mainfabric disposed on a the central section of the balloon, a first fabrichaving only interweaved first fibers disposed on the tapering end, and asecond fabric having only interweaved second fibers disposed over thefirst fabric.

In each of the above-described embodiments, the first fabric, layer, orfabric layer can separate into an inner first fabric, layer, or fabriclayer and an outer first fabric, layer, or fabric layer to reinforce theballoon. The second fabric, layer, or fabric layer can be separated intoan inner second fabric, layer, or fabric layer and an outer secondfabric, layer, or fabric layer to reinforce the balloon. The main orcentral portion of the balloon can define a cylinder and the first,second, end, or tapering portions can define cones. The main fabric,layer, or fabric layer can also connect to the first and second fabriclayers proximate to a transition between a cylindrical portion of theballoon and a cone section of the balloon. Also, each of theabove-described embodiments can have the balloon engaging a catheter,the balloon engaging an implantable device disposed around the exteriorof the balloon, and the balloon engaging a stent disposed around theexterior of the balloon.

Also, the method of manufacturing a medical balloon includesinterweaving first and second fibers to weave a main fabric to reinforcea central section of the balloon, interweaving only the first fibers toweave a first fabric to reinforce a tapering end of the balloon havingan outer diameter the is less than an outer diameter of the centralsection, and interweaving only the second fibers to weave a secondfabric to reinforce the tapering end of the balloon by disposing thesecond fabric over the first fabric. This method can include weaving thefirst fibers to form an inner first fabric and an outer first fabric toreinforce the tapering end of the balloon, weaving the second fibers toform an inner second fabric and an outer second fabric to reinforce thetapering end of the balloon, forming the central section of the balloonto define a cylinder and forming the tapering end of the balloon todefine cones, and weaving the main fabric to join the first and secondfabrics proximate to a transition between a cylindrical portion of theballoon and a cone section of the balloon.

The balloon and fibers are preferably polymers, and attached to theballoon base by an adhesive. Longitudinal fibers preferably runsubstantially parallel to the longitudinal axis of the balloon. Themethod preferably includes heating a thermopolymer to embed anlongitudinal array of fibers in a matrix covering a tube. The methodpreferably also includes inflating an untwisted tube in a mold beforewinding hoop fiber and including heating a thermopolymer to embed thelongitudinal array of fibers in a matrix covering the inflated tube.

According to yet another preferred embodiment, a method of forming afiber reinforced balloon, comprises: holding an array of longitudinalfibers on the surface of a vessel to be reinforced while simultaneouslywrapping a hoop fiber helically around the array of fibers to form ahelix which crosses the longitudinal fibers at substantially rightangles.

Preferably, the wrapping includes circling a bobbin, which holds thehoop fiber, around the vessel. The holding can be performed by an arrayof spring biased fiber feeders. The method preferably also includesapplying a curable coating to the fibers after the wrapping andsubsequently curing the curable coating to form an outer surface. Themethod preferably also includes applying an adhesive to the surface ofthe vessel prior to holding and wrapping.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated herein and constitutepart of this specification, illustrate exemplary embodiments of theinvention, and, together with the general description given above andthe detailed description given below, serve to explain the features ofthe invention.

FIG. 1A illustrates an exemplary braid pattern that transitions from onelayer to two layers.

FIG. 1B schematically illustrates an edge on view of the braid patternof FIG. 1A.

FIG. 2 schematically illustrates a fabric having a braid pattern thattransitions from a single layer to multiple layers and a cross-sectionalprofile of an end of a balloon.

FIG. 3 is an isometric illustration of balloon reinforced with the braidpattern of FIGS. 1A, 1B, and 2C.

FIG. 4 illustrates device for forming a braid pattern of a fabric on athree-dimensional surface of a balloon.

FIGS. 5A through 5E illustrate exemplary manufacturing steps for forminga nonwoven or woven fiber-reinforced fabric for a balloon.

FIG. 6 illustrates an apparatus for disposing fibers on a mandrel orbase structure.

FIG. 7 illustrates an alternative apparatus for disposing fibers on amandrel or base structure.

MODE(S) OF CARRYING OUT THE INVENTION

As illustrated in FIGS. 1A and 1B, an exemplary fabric 10 has a triaxialstructure with fibers 11 a, 11 b, 11 c, 11 d, 11 e, 11 f disposed inthree directions to form a braid of the fabric 10. Fibers 11 a, 11 b, 11c are illustrated without shading and fibers 11 d, 11 e, 11 f areillustrated with shading. Fabric 10 has two portions: a single-layerportion 12 a where the fibers 11 a, 11 b, 11 c, 11 d, 11 e, 11 f areinterwoven to form the fabric 10 with a single layer 18, and a two-layerportion 12 b where the fibers 11 a, 11 b, 11 c are interwoven to form afirst layer 20 of the fabric 10 and the fibers 11 d, 11 e, 11 f areinterwoven together to form a second layer 21 of the fabric 10. As alsoillustrated in FIG. 1A, it can be seen that layers 20 and 21 areidentical in terms of the braid pattern and offset relative to eachother.

The boundary where the fabric 10 transitions from the single-layerportion 12 a to the two-layer portion 12 b is a transition line 22. Ascan be appreciated from FIGS. 1A and 1B, the fiber density of thesingle-layer portion 12 a is twice the fiber density of either layers 20or 21. It can also be appreciated that the weave patterns of each of thefirst and second layers 20, 21 are disposed to continue withoutinterruption the weave patterns established by the shaded and unshadedfibers in the single-layer portion 12 a. The schematic side view in FIG.1B shows, edge-on, how the first layer 20 and second layer 21 join toform the single layer 18 at the transition line 22. As can alsoappreciated, the division of single layer 18 into first layer 20 andsecond layer 21 can be repeated by further dividing one or both of firstand second layers 20, 21 into additional layers at additional transitionlines. It can also be appreciated that the single-layer portion 12 a canbe divided into more than two layers by, for example, having the sixfibers Hal 1 f divide into three layers that each have two of the sixfibers 11 a-11 f, or into six layers that each have one of the sixfibers 11 a-11 f. It is also contemplated that the single-layer portion12 a could divide into layers that have a differing numbers of fibers,such as a first layer with four of the six fibers 11 a-11 f and a secondlayer with two of the six fibers 11 a-11 f.

FIG. 2 is a schematic illustrating multiple transitions in a fabric 30from a single layer structure having a layer 32 to two-layer structurehaving a layer 34 and a layer 36, and then again having a transition inwhich layer 34 divides into layers 42, 44 and layer 36 divides intolayers 38, 40 to form a four-layer structure of fabric 30.

As can be appreciated, the braiding pattern of fabrics 10, 30 may beconstructed to follow a shape, such as the conical end of a medicalballoon 46, as schematically illustrated in FIG. 2. Balloon 46 can havea diameter that decreases progressively from diameter D1 over acylindrical portion 50 of the balloon 46 to a range of smaller diameterssuch as diameters D2, D3, D4 in a conical portion 52 of the balloon 46.The diameters D2, D3, D4 mark transition lines 22 where a layer dividesinto two layers, such as where layer 32 branches into layers 34, 36. Thetransition lines 22 can follow other balloon diameters and shapes usingthe same layer division mechanism to control the density of the yarns ineach layer. The transition lines 22 can also be disposed in a balloonwith varying geometries, such as a balloon with a cylindrical portion 50having a portion with a diameter that is less than diameter D1, or withprotrusions extending from the balloon, or with other features that varythe cross-sectional shape and dimensions of the balloon. Also note thatalthough the embodiments discussed herein focus on balloons, thebraiding and layer dividing technique described herein can be applied toother kinds of structures, including non-pressure holding structuressuch as stents, grafts, or composite articles of manufacture.

As shown in FIGS. 1A-2, when the same fibers 11 a-11 f are divided amongmultiple layers, the fiber density per layer is reduced, which allowsthe braid of the fabric of each layer to conform to a smaller diameterof the balloon without causing the fibers or layers to bunch or jam dueto the decreasing circumferential area of the balloon. For example, thefabric 30 can be wrapped over a structure with a reducing diameter, suchas at conical portion 52, without causing the fibers of each layer inthe fabric 30 to bunch up or create an undesirably high fiber density atsmaller diameters. The exemplary braiding and layer dividing techniquedescribed herein thus advantageously allows for a fabric with a singlecontinuous braid structure to be formed over an entire balloon whilealigning the braid fibers in a preferable geodesic arrangement. Theexemplary dividing technique also facilitates the control of fiberdensity and the arrangement of layers when the fabric is disposed in avariety of shapes such as, for example, a conical section 52 having asaddle (S-shaped, serpentine, or hyperboloid profile) or spheroidalshape.

FIG. 3 illustrates a balloon 100 with a balloon base 90 having a fabric60 with a single layer region 102 disposed in a central cylindricalportion 91 of the balloon 100 and including a portion of tapered regions101, 103, and double layer regions 104, 112 disposed in each of thetapered regions 101, 103, respectively. Quadruple layer regions 106, 114extend toward the extreme ends of the balloon 100 at the taperedportions 101, 103.

A preferred method of forming a braid of a fabric which transitions fromsingle to multiple layers is schematically represented in FIG. 4. Abraiding machine 170 has floating bobbins 140 a, 140 b, 141 a, 141 b,142 a, 142 b each controlling the disposition of fibers 148 a, 148 b,149 a, 149 b, 150 a, 150 b. The bobbins are moved by a conveyor table172 which is preferably a Cartesian-type braiding machine employing aCartesian braiding process. A Cartesian braiding process is capable ofproducing multiple layer or single layer braids of any desired braidstructure and allows the formation of the braid structure to change asthe fabric is being made, i.e., on the fly. Generally the preferredbraid structures are laid out in a two dimensional pattern over athree-dimensional surface and capable of changing as the braid structureextends in an axial direction 92 of the fabric 60, balloon base 90, orballoon 100. The braiding machine 170 moves the bobbins 140 a, 140 b,141 a, 141 b, 142 a, 142 b on a machine bed (not shown) according to apreset program that permits the creation of transition lines 122 wherethe layering of the fabric 60 changes between single layer region 102,double layer regions 102, 114, and quadruple layer regions 106, 114.Bobbin-passing mechanisms (not shown) shuttle the bobbins 140 a, 140 b,141 a, 141 b, 142 a, 142 b around a planar array (not shown) to allowthe bobbins to pass around each other in such a manner as to create thebraid, and to create transition lines 122. Six bobbins 140 a, 140 b, 141a, 141 b, 142 a, 142 b are shown in the drawing although a fewer orgreater number of bobbins can be used to form a fabric with a variety ofbraid structures.

Note that although the term “Cartesian” is used, this is not intended tolimit the preferred method and apparatus for making the braid to ones inwhich the bobbins follow rectilinear paths or rectilinear arrays ofstations. For example, for balloons with round cross-sections, it maydesirable for the bobbin transferring mechanisms to define polararrangements of bobbin passing mechanisms. So it should be understoodthat Cartesian-type braiding machines, as the characterization is usedherein, may encompass any type of bobbin-passing device. Also note thatthe braid may be formed by mechanisms other than such a Cartesian-typedevice.

In a Cartesian-type braiding machine 170, fibers 148 a, 148 b, 149 a,149 b, 150 a, 150 b are disposed on balloon base 90 in a braidingpattern that transitions from a single layer to multiple layers bymoving three bobbins 140 a, 141 a, 142 a around the circular conveyortable 172 in any desirable sequence to form a first braided layercorresponding to first layer 20 on the base balloon 90. Bobbins 140 b,141 b, 142 b are also moved around conveyor table 172 to form another asecond braided layer corresponding to second layer 21 on the baseballoon, possibly over the first layer 20, so that the fibers 148 b, 149b, 150 b do not interweave with fibers 148 a, 149 a, 150 a. Two separatebraided layers are thus formed. The balloon base 90 is also movedrelative to the conveyor table 172 as the braided layers areprogressively formed and, when the transition line 122 is to be formed,the bobbins 140 a, 140 b, 141 a, 141 b, 142 a, 142 b move to cause thefirst braided layer and the second braided layer with be interwoven toform a single braided layer corresponding to single layer 18. Thereverse of this process can be performed as well, with the fabric 60transitioning from a single braided layer to multiple braided layers. Avarying number of layers can be formed with a suitable number of bobbinsand a sufficient array of trajectories for the bobbins to follow.

The trajectory of the fibers may be controlled by controlling the feedrate of the balloon base 90 relative to the movement of the bobbins, asis known in the art of Cartesian and other types of braiding systems.Note that although a cylindrical structure having the form of a medicalballoon is shown by way of example, other shapes of balloons or otherstructures can be reinforced using the structures and methods described.

One type of mechanism for moving the bobbins employs rotating elementsthat are fixed at an array of stations, and the rotating elements haverecesses that pass the bobbins from station to station. Bobbins can beprogrammed to move in any course over the whole plane of the conveyorplane 172. If correspondingly programmed, a single braided layer can bemade to transition to a two braided layers without any interruption. Thebobbin-passing mechanism of the Cartesian braiding machine can be formedwith a hole 130 in the center of conveyor table 172 to allow acylindrical mandrel (not shown) to pass through and facilitate theweaving of the braided layers around the mandrel.

Circular looms and other automated fabric manufacturing techniques poseproblems for high performance thin-walled structures such as medicalballoons. It is believed that it can be difficult to form a helical orlongitudinal fiber pattern over a balloon base or mandrel with a varyingcross-section. It is also believed that looms that require a shuttlebobbin cannot be used with a varying balloon base or mandrelcross-section without the use of a complex mechanism to pass the shuttlebobbin and an additional device to perform a beater function ofdensifying the weft yarns. Also, friction between fibers can causeproblems, particularly when the fibers are very thin. It is alsobelieved that braiding is made difficult when there is a need forweaving, managing variations in the balloon base or mandrel diameter,and maintaining geodesic yarn trajectories.

It is believed that placing fibers without interweaving overcomes someof the difficulties associated with weaving and braiding found inexisting techniques. Fibers may be aligned in the longitudinal and hoopdirections to avoid problems with respect to geodesic alignment andcircular looms. The exemplary dividing technique and layering also hasthe advantage of limiting friction during manufacturing because frictionbetween fibers is reduced because few fibers are interlaced with eachother to form the fabric. Also, smoother trajectories followed in anon-woven arrangement is believed to enhance strength and reduce stretchof the fabric.

Another method for making a balloon with fibers is illustrated in FIGS.5A-5D. As shown in FIG. 5A, a tube 202 is wrapped helically with fibers201. The surface of the tube 202 is preferably first coated with anadhesive. The tube 202 is preferably of a material that has lowelasticity in the axial direction of the tube so as to stretch primarilyin the circumferential direction. Also, prior to wrapping the fibers201, the tube 202 is preferably twisted a predetermined distance aboutits longitudinal axis such that an elastic torsion is generated withinthe wall of the tube 202. It is believed that a tube made of a materialwith anisotropic elastic properties and formed so as to be inelasticalong its longitudinal axis will tend to shorten when twisted in acircumferential direction about the longitudinal axis of the tube. Whenthe tube 202, with the fibers adhered thereto, is subsequently untwistedas shown in FIG. 5B, the fibers 201 become aligned with the longitudinalaxis of the tube 202.

Referring to FIG. 5C, the tube 202 is thereafter expanded by inflationin a mold 206 that causes the tube 202 and attached fibers 201 to expandto form a reinforced balloon base 210. The tube 202 and fibers 201 areinelastic in the axial direction of the tube 202, which causes thelength of tube 202 to shorten as it is circumferentially expanded in themold 206 to form reinforced balloon base 210. The mold 206 may be linedwith a thermopolymer before encapsulating the tube 202 within the mold206 and the mold can be heated to facilitate the fixing of the fibers201 to the thermopolymer coating. All or a portion of the tube 202 canbe subsequently removed from the reinforced balloon base 210, or aninternal mandrel to the tube 202, if used, can be removed if desired.

In alternative to the thermopolymer coating, any chemically curableplastic coating can be applied to the mold 206 recess so that the fibers201 are pressed into the coating by the expansion of the tube 202 whenforming the reinforced balloon base 210. Alternatively the mold 206 mayhave porous recesses that permit injection of a curable material into aspace between the fibers 201 and the tube 202.

Once the reinforced balloon base 210 with longitudinally-disposed fibers201 is formed, a helical wind 219 may be formed around the reinforcedballoon base 210 by rotating the reinforced balloon based 210 andfeeding a fiber over it tangentially from an axially advancing bobbin,to form balloon 220 as illustrated in FIG. 5D. Preferably, thereinforced balloon base 210 is first coated with a material to preventthe helical wind from slipping. In another embodiment, two helical winds219 are applied to the reinforced balloon base 210 with symmetrichelical angles relative to the longitudinal axis of the balloon or toeach other, to form balloon 221 as illustrated in FIG. 5E. The twohelical winds 219 can be disposed sequentially, without weaving, orsimultaneously in a weaved pattern.

Preferably multiple balloons are created at once from a single long tube202. The tube may be expanded into the mold 206 and advanced to createadditional balloons 210 or multiple molds 206 may be supported in alongitudinal array to create multiple balloons 210 at once. A singlehelical wind can be created over multiple balloons 210 to achievemanufacturing economies over a single-balloon manual method.

FIG. 6 schematically illustrates a weaving device 250 for laying fibersover a mandrel or balloon base 190 to form balloon 220. The mandrel orballoon base 190 is moved through a longitudinal fiber feeder 200 in theweaving process by an axial drive 204 and axial drive transmission 203.The longitudinal fiber feeder 200 feeds longitudinal fibers 222 fromlongitudinal fiber spools 208 onto the mandrel or balloon base 190. Atthe same time, a helical fiber feeder 224 which orbits on a track 225winds a helical fiber 230 in a weave with the longitudinal fibers 222laid onto the mandrel or balloon base 190 by the longitudinal fiberfeeder 200. A feeder support 228 stems from a shuttle 216 having ahelical fiber spool 214 which is driven by a shuttle drive 242 andtransmission 240 around the circular track 225. The mechanism fordriving the shuttle 216 can be any suitable mechanism, such as is usedfor driving the shuttle of a circular loom. The fibers may be held intension by feeder supports 212 for the longitudinal fibers 222, and byfeeder support 228 for the helical fiber 230. The feeder supports 212,228 can be tubes or guide wires or any suitable device for guiding thefibers as they unwind from the respective spools 208, 214.

The feeder supports 212 are arranged to follow the surface of themandrel or balloon base 190 and are preferably positioned such thattheir tips are close to the mandrel or balloon base to position thelongitudinal fibers 222 as it is laid onto the mandrel or balloon base190. The curved surface of the mandrel or balloon base 190 is followedby the tips of the feeder supports 212 so that the longitudinal fibers222 do not extend or bridge substantially to reach the surface of themandrel or balloon base 190. The longitudinal fibers 222 are drawn asthe mandrel or balloon base 190 moves axially relative to thelongitudinal fiber feeders 200. Thus, as the mandrel or balloon base 190advances, the longitudinal fibers 222 are laid in place and the helicalfiber 230, which is spooled in a circumferential pattern and naturallydrawn into a helix-shaped wind as the mandrel or balloon base 190advances, holds the longitudinal fibers 222 in place against the surfaceof the mandrel or balloon base 190. Preferably, the mandrel or balloonbase 190 is provided with a tacky or non-slip coating to prevent thehelical wind from slipping off.

FIG. 7 shows a weaving device 260 similar to that of FIG. 6 from anend-facing point of view along the longitudinal axis of the weavingdevice 260. In this embodiment, the longitudinal fibers 272 are fed frommultiple spools 270 which fully surround the mandrel or balloon base255, though only a few are illustrated in FIG. 7. The weaving device 260includes an iris 262 which circumferentially expands and contracts tomaintain the position of the longitudinal fibers 272 close to themandrel or balloon base 255. The iris 262 may be designed to passivelycontrol the position of the longitudinal fibers 272 with springs orbiasing blades 263 the maintain contact with or a close proximity to themandrel or balloon base 255. Alternatively the iris 262 may beconfigured by a suitable drive mechanism based on feedback from amechanical or optical profile follower or made programmable bysynchronizing the iris 262 with the movement of the mandrel or balloonbase 255 having a predetermined profile. A helical fiber 266 is fed froma spool 265 on a shuttle 264 which circles the mandrel or balloon base255 along a path of travel 268 as the mandrel or balloon base 255 ismoved in the axial direction normal to the plane of FIG. 7.

Various additional details of the described embodiments, such as howbase balloons may be used or other various types of mandrels, aredescribed in International Application No. PCT/US07/81264, which ishereby incorporated by reference in its entirety herein as if fully setforth herein.

As described in International Application No. PCT/US07/81264, a moldillustrated in FIGS. 7 and 8A-8C may be used to melt a matrix aroundfibers to form a balloon. In one method, the fibers are coated with amatrix-forming material that flows at a lower temperature than the basematerial of the fibers. For example high melting-temperature fibers maybe coated with low melting-temperature thermoplastic. Then a pre-formmay be formed either by braiding over a collapsible mandrel with thetwo-part fibers. The mandrel with the preform is then placed in the moldand heated to melt the low melting temperature material but leave thefibers intact. The mold is then removed and the mandrel can be collapsedor disintegrated to remove it, leaving the fully formed balloon with thespaces between the fibers filled with the low melting temperaturematerial of the original fibers. The mandrel can be made of glass,metal, wax, or rigid or flexible polymer, for example, and removed bydeflating or by dissolving with acid, for example.

As another alternative, the starting fibers could be a two-part fiberwith one part, for example, a coating of a chemically hardenable orcurable material. Instead of heating in the mold, the pre-form could besprayed with a chemical hardener and molded until hardening occurs, asdescribed in International Application No. PCT/US07/81264 at FIGS. 7 and8A-8C. The mandrel could then be removed in a manner set forth in theprevious embodiment.

Note that the proportions of the articles and precursors (parisons)shown in the figures are not intended to be representative of apractical medical balloon and are chosen for the purpose ofillustration. While the present invention has been disclosed withreference to certain embodiments, numerous modifications, alterations,and changes to the described embodiments are possible without departingfrom the sphere and scope of the present invention, as defined in theappended claims. Accordingly, it is intended that the present inventionnot be limited to the described embodiments, but that it has the fullscope defined by the language of the following claims, and equivalentsthereof.

I claim:
 1. A medical balloon comprising a plurality of continuousinterwoven fibers, said fibers forming a fabric which defines only asingle layer on a first section of the balloon and multiple layers on asecond section of the balloon.
 2. The medical balloon of claim 1,wherein the multiple layers on the second section include at least twolayers which are separate from and adjacent to one another.
 3. Themedical balloon of claim 1, wherein the fabric transitions from thesingle layer to the multiple layers at a transition line.
 4. The medicalballoon of claim 1, wherein the multiple layers each include an equalnumber of fibers.
 5. The medical balloon of claim 1, wherein themultiple layers each include an unequal number of fibers.
 6. The medicalballoon of claim 1, wherein the multiple layers comprise an inner layerand an outer layer.
 7. The medical balloon of claim 1, wherein the firstsection of the balloon has a larger diameter than the second section ofthe balloon.
 8. The medical balloon of claim 7, wherein the balloon isdisposed along a longitudinal axis, and the first section is disposedalong a central portion of the longitudinal axis and the second sectionis disposed along an outer portion of the longitudinal axis.
 9. Themedical balloon of claim 7, wherein the balloon is disposed along alongitudinal axis, and the first section is disposed along an outerportion of the longitudinal axis and the second section is disposedalong a central portion of the longitudinal axis.
 10. A medical ballooncomprising: first and second fibers at least in part interwoven togetherto define a main layer that reinforces a main portion of the balloon,the first fibers defining a first layer than that reinforces a firstportion of the balloon, the second fibers defining a second layer thatreinforces the first portion; wherein the first layer is separate fromthe second layer.
 11. The medical balloon of claim 10, wherein the firstlayer is an inner layer and the second layer is an outer layer.
 12. Themedical balloon of claim 10, wherein the first layer and second layerinclude equal numbers of fibers.
 13. The medical balloon of claim 10,wherein the first layer and second layer include unequal numbers offibers.
 14. The medical balloon of claim 10, wherein the main portion ofthe balloon has a larger diameter than the first portion of the balloon.15. The medical balloon of claim 14, wherein the first and second layershave a lower fiber density than the main layer to minimize jamming ofthe fibers.
 16. A method of manufacturing a medical balloon, comprising:interweaving first and second fibers to form a main fabric layer toreinforce a main balloon section; interweaving only the first fibers toweave a first fabric layer to reinforce a first balloon section; andinterweaving only the second fibers to weave a second fabric layer toreinforce the first balloon section by disposing the second fabric layerover the first fabric layer.
 17. The method of claim 16, wherein theinterweaving of fibers is done through a Cartesian braiding process. 18.The method of claim 16, wherein the interweaving of fibers is donethrough a polar braiding process.
 19. The method of claim 16, furtherincluding the step of forming a continuous transition between the mainfabric layer to each of the first and second fabric layers.
 20. Themethod of claim 16, wherein the main balloon section has a main diameterand the first balloon section has a first diameter which is smaller thanthe main diameter.